Paper pulp screen



PAPER PULP SCREEN 5 Sheets-Sheet 1 Filed Jan.. 26, 1945 m. m vm r w 8 8 7 WI] 1 8 a an a 4 7 6 a a w mwa 0 .o. w 3 a a wj red 1 Maifiewso by M M QQnM/ Oct. 5, 1948. w. F. MATHEWSON 2,450,833

PAPER PULP- SCREEN Filed Jan. 26, 1945 5 Sheets-Sheet 2 Iaweaa'oa uifforneys Oct; 5, 1948.

W. F. MATHEWSON PAPER PULP SCREEN 5 Sheets-Sheet 5 Fil ed Jan. 26, 1945 Oct. 5, 1948. w. F. MATHEWSON I I 2,450,838

PAPER PULP SCREEN Filed Jan. 26, 1945 5 Sheets-Sheet 4 Patented 6on5, 1948.

' OFFICE .2,450,838 PAPER PULP SCREEN Wilfred FsMathewson, Weymouth, Mall. Application January 26, 1945, Serial No. 574,789

.1 This invention relates to pulp screens, and it has for one of its objects to provide a novel screen which is capable of an increased output as compared with other screens of the same size.

Another object of the invention is to provide a novel pulp screen which will screen the pulp to a given size of fibre with a high degree of accuracy.

A further objectof the invention is to provide anovel means for keeping the screening elements clean and free from accumulated refuse or rejects.

Still other objects of the invention are to improve generally pulp screens ln various ways as will be hereinafter set forth.

In attaining these objects, I have provided a pulp screen in which the screening means is constituted by two parallel walls separated by a small clearance space which is of sufficient size to permit the fine acceptable portion of the unscreened pulp to pass therethrough .but which is insufiicient in size to permit the coarse material or refuse to pass, one of said walls being provided .with a plurality of pockets or grooves, all of which open into the clearance'space, and in which the unscreened pulp is delivered by means other than the clearance space to certain of said grooves or pockets, the remaining grooves or pockets being .connected by means other than the clearance space to a screened pulp outlet. For convenience I will refer to the grooves or pockets to which the unscreened pulp is delivered as grooves" or inlet pockets and will also refer to the grooves or pockets which communicate with the screened pulp outlet as the discharge grooves or discharge pockets." Both the inlet grooves or pockets and the discharge grooves or pockets communicate with the same clearance space, and in the screening operation, the pulp which is delivered to the inlet pockets tends to flow into the discharge pockets through said clearance space, but as the latter is of a size to permit only the fine acceptable portion of the pulp to pass therethrough and is of insufficient size "to permit the coarse material to pass, the result will be that only the fine acceptable portion of the pulp will flow from the inlet pockets to the discharge pockets through said clearance space. 1 1

Any coarse unacceptable portion of the pulp which cannot pass throughthe clearance space will tend to clog the latter, and I have provided novel means for periodically flushing such clearance space to flush out of it any accumulation of coarse unacceptable material.

13 Claims. Cl. 92-45) inlet 2 In order to give an understanding of the invention, I have illustrated in the drawings a selected embodiment thereof which will now be described, after which the novel features will be pointed out in theappended. claims.

In thedrawingsr- Fig. '1 is a vertical sectional view of a pulp screen embodying my invention, said section being taken on the line l-l, Fig. 2.

Fig. 2 is a horizontal sectional view on the line 2-2, Fig. 1. v

Fig. 3 is a fragmentary vertical sectional view.

Fig. 4 is a section on the line 4-4, Fig. 3.

Figs. 5. 6, and 7 are fragmentary transverse sectional views through the screening elements illustrating the screening and screen-cleaning operations.

Fig. 8 is an Fig. 3.

Fig. 9 is an enlarged section on the line 9-9, i 3. r

Fig. 10 is a fragmentary view showing the out-- enlarged section on the line 88,

side of the screening element 8;

Fig. 11 is a fragmentary sectional perspective view showing a portion of the inside oi the outer screening element 8, said view showing a section taken through the inlet pockets or grooves ill;

Fig. 12 is a view similar to Fig. 11, but showing the section taken through the outletpockets or grooves ii.

The pulp screen herein illustrated comprises a casing member i. herein shown as cylindrical-in cross section and which is provided at its upper end with a head 2 having an inlet 3 for the unscreened pulp. Said casing is also providedat its lower end with a base or lower head'l provided with an outlet 5 for'the screened pulp and a second outlet 6 for the tailings or rejects.

The screening means of my improved pulp screen is located within the casing l and is constituted by two screen members which present two parallel walls separated from each other by a small clearance space that is of sumcient size to permit the fine acceptable portion of the pulp to pass therethrough but is insufflcient in size to permit the coarse unacceptable portion of the pulp to pass. One of these screening members is provided with a plurality of grooves or pockets in its wall which bounds the clearance space, certain of said pockets or grooves having communication with the unscreened pulp inlet 3 and the remainder of said pockets or grooves having communication with the screened pulp outlet 5.

These screen members are shown as cylindrical 65 members arranged concentrically. The two aesaeas screen members are constituted by an inner cylin= drical member l and an outer cylindrical memoer G, said cylindrical membershaving a com mon axis and thereby being concentric. The outer "wall or" the inner member l and the inner wall of the outer member 8 are spaced apart so as to provide a small clearance space 9 which is of a size to permit the fine acceptable portions of the pulp to pass through but is insufllcient in size to permit the coarse unacceptable portions of the pulp to pass.

One of the screen members, the outer member 8 in the present embodiment of the invention, is provided in the wall thereof which bounds the clearance space 9 with a plurality of pockets herein shown in the form of vertical grooves. Some of these pockets have communication with the pulp inlet 3, while the remainder of the pockets have communication with the screened pulp outlet 5. I will preferably arrange these grooves or pockets in circumferential rows and in such a way that every other pocket in any row communicates with the inlet 3 while the other pockets communicate with the screened pulp outlet 5, In other words, the successive pockets or grooves communicate alternately with the inlet 3 and the outlet 5, and all the pockets or grooves also communicate with the clearance space.

The grooves which communicate with the inlet 3, and which for convenience are referred to as inlet grooves are indicated at III, while the other grooves which communicate with the screened pulp outlet 5 and which for convenience are referred to as discharge grooves are indicated at II. Each inlet groove Ill, therefore, has on each side thereof a discharge groove I I and the communication between any inlet groove I0 and the adjacent discharge grooves II is through the clearance space 9.

These grooves I0 and II may extend the full length of the outer member 8, but I will preferably provide said member with a plurality of rows of shorter grooves, each row of grooves extending circumferentially.

The outer screen member 8 is shown as composed of an outer section I2 and an inner section, which in turn is composed of a plurality of annular ring like members I3. The inner face of each ring member I3 is formed with the grooves I0 and II, and the outer face of each ring member is provided with an annular rib I4 which is secured to the outer section 8 by means of attaching screws I5. The outer section 8 is formed with circumferential bulged portions I6 which with the ring members I3 and the ribs l4 provide a plurality of circumferential chambers II, I8. The grooves I0, II are so formed in each ring member I3 that of any two adjacent grooves, one of them will communicate with an annular cham her I! while another will communicate with an adjacent annular chamber I8. The grooves III, II are shown as being of progressive depth from one end to the other, the deep end of each groove opening into one of the chambers I! or I8. Reierring for instance to Fig. 3, the ring member I3a has in it the rows of vertical grooves, the grooves I0 opening into the annular chamber I'I while the other grooves II open into the annular chamber I8.

Means are provided whereby unscreened pulp may be delivered to the various annular chambers I1 and by which the various annular chambersB l8 are connected to the screened pulp outlet For convenience I will. refer to the a u r 1 chambers i? as inlet chambers and to the anhula: chambers it? as discharge chambers."

The unscreened pulp which is delivered to the inlet chambers ill will pass through the inlet grooves of the various ring members It? and the an eptable portion of the pulp will pass through the clearance space 9 into the discharge grooves ill, from which the pulp is delivered to the annular discharge chambers I8 and from the latter to the screened pulp outlet 5. The means by which the unscreened pulp is delivered to the annular inlet chambers I1 and the screened pulp is delivered from the discharge chambers I8 to the screened pulp outlet 5 is as follows. The space between the outer screen member 8 and the casing i is divided by vertical partitions I8 into a plurality of vertical passageways 20, 2!. The casing i is provided at its upper end with a transverse partition 22 which has openings 23 therein that communicate with the vertical passages 20 only, so that unscreened pulp may flow from the inlet 3 into said passages'20 only. For convenience, these passages 20 will be referred to as inlet passages.

The outer section l2 of the screen member 8 is provided with openings 24 in the outer wall of each annular inlet chamber H, which openings 24 register with the vertical inlet passages 20 and provide communication between said inlet chambers I1 and the inlet passages 20. The lower ends of allthe vertical passages 20' are closed by a horizontal partition 25.

The inner screen member I is formed with a top 28 which, together with the partition 22, constitutes the bottom of an annular chamber 28 with which the inlet 3 communicates so that the unscreened pulp delivered to the inlet 3 will fill the chamber 29 and flow through the openings 23 into the vertical passages 20 and from these through the openings 24 into the inlet chambers ll'. From the inlet chambers I I the pulp flows through the inlet slots or gr v 0 into the clearance space 9, and the acceptable portion of the pulp will flow through the clearance space around into the discharge grooves or slots II, which, as stated above, comm nicate with the annular discharge chambers I8. ese discharge chambers I6 communicate with the vertical passages 2I through openings or ports 30 which are formed in the outer section I2 of the screen member 8, and. therefore the acceptable portion of the pulp which ,passes through the clearance I space into the discharge grooves II will be delivered into the annular chambers I8 and from these into the vertical passages 2|. For convenience the vertical passages 2| are referred to as' discharge pas-sages.

'The horizontal partition 25 is provided with ports 26, one for each discharge passage 2|, which ports lead into the annular sump 21 with which the base i is provided and which in turn communicates with the screened pulp outlet 5.

It will be observed that the means by which the unscreened pulp is delivered to the inlet pockets or grooves i0 is separate from the clearance space, and similarly the means provided for delivering the screened pulp from the discharge grooves or pockets I I to the screened pulp outlet is separate from the clearance space.

It will also be observed that the unscreened pulp is delivered to the clearance space, and the screened pulp is delivered therefrom through pockets or passages formed in the same wall which forms one side of the clearance space.

This screening operation is illustrated in the Figs. 5, 6, and 7. In these fragmentary sectional.

the annular discharge chambers l8.

the discharge grooves Wbut insufllcient'in size Any coarse material or unacceptable portion of the pulp such as shown at 3| in Fig. 6 which cannot passthe clearance space 9 will tend to accumulate in the mouth of the inlet groove lliand thus clog the groove. To prevent any such clogging or the groove, 1 have provided for periodically flushing out each inlet groove so as to remove therefrom any of the 'tailings or unacceptable portion of the pulp. This is done by providing the inner screen member 1 with aplurality of openings or slots 32 which extend vertically thereof, and by rotating said inner member within the outer member.

As each slot 32 of the inner member moves past the various inlet grooves Hi, the pulp will tend to flow from each groove l0 through the slot 32 into the interior of the inner member I. This member 1 is open at its bottom and the lower head 4 is provided with a well 33 which communicates with the interior of themember l and with the tailings outlet 6.

If at any time any coarse or refuse material such as indicated at 3! tends to accumulate-at the open end of any inlet groove ID as shown in Fig. 6, then when the next slot 32 of the member 1 registers with said clogged slot, the refuse material will be flushed out of the groove through the opening 32, as shown in Fig. 7, and into the interior oi the said member 1 from which. it will pass through the tailing-s outlet 6. Each inlet groove l0, therefore, is periodically flushed out by the rotative movement of the member I and thus the screen is kept free and in an unclogged condition without the use of any mechanical scrapers or screen-cleaning blades. The slots 32 in the member 1 are made wider at the inner face of said member than at the outer face thereof, thereby providing relatively sharp knife-like edges 43. Such sharp edges act somewhat as knives to help loosen any coarse material or rejects which have dammed up the open side of any inlet slot l0, thus assisting the flushing operation. I

Any suitable means will be employed for rotating the inner member I. In the illustrated embodiment of the invention, the head 28 of said member .1 is provided with a vertical shaft 34 which is mounted in suitable bearings in the head I 2 and is provided at its upper end with a worm gear 35 that meshes with a worm 36 on a shaft 31, said shaft being connected by a sprocket chain or belt 38 with a shaft 39 also mounted in bearings in the head 3. The shaft 39 has a pulley l0 thereon which is driven by means of a belt 4| from a suitable motor 42 also mounted on the head 2.

The means for rotating. the inner member 1 may be such as to give said member either a continuous rotation or an intermittent or step-bystep rotation. In either case, however, the rotative movement of the inner member brings each slot 32 therein into register with the inlet slots l 0 successively so that each inlet slot is subjected periodically to a flushing operation which keeps it clean. The member 1 may be rotated in either direction.

From the above it will be observed that I have herein provided a novel pulp screen in which the screening element comprises two opposed walls spaced from each other to provide a clearance space suflicient in size to permit the acceptable portion ofunscreened pulp to pass therethi'ough to permit the unacceptable to pass, one of said walls pockets, certain of which unicate with the pulp inlet and the remaines of which communicate with a screened pulp outlet, whereby the pulp is screened by passing into the first-named pockets, through the clearance space and into thelast-named pockets and from thence to the screened pulp outlet. The pockets or slots id and H together with the annular chambers i1 and I8 into which the pockets or slots open, provide openings extending through the outer screen member 8, the slots l0 and the chamber li constituging inlet openings through which the unscreen d pulp flows from the inlet passages 20 on t e outside of the screen member 8 into the clearance space, 8, and the slots H and chambers l8 constitutingdischargeopenings through which the screened pulp flows from the clearance space to the discharge passages 2l that are also situated on the outside of the screen member 3.

The movement of the unscreened pulp into the clearance space and the movement of the screened pulp from said clearance space is therefore through openings in the same wall though in opposite directions. In other words, the unportion of such pulp having a plurality of com screened pulp flows through the outer screen member 8 from the outside to the inside while the screened pulp flows through said screen member 8 from the inside to the outside.

It will also be observed that my inventio nprovides a novel construction by which the pockets can be periodically flushed so as to keep them clean from accumulated refuse material.

, I claim:

1. A pulp screen comprising a casing having an inlet and a screened pulp outlet, pulp-screening means within the casing comprising two screen members separated by a clearance space bf sufficient size for the acceptable portions of unscreened paper pulp to pass therethrough but insuflicient in size for the unacceptable portion of such pulp to pass therethrough, one of said members having a plurality of grooves in the face thereof which bounds said clearance space.-a portion of said grooves constituting inlet grooves and the remainder of the grooves constituting discharge grooves, means for delivering unscreened pulp from said casing inlet to the inlet grooves, and means providing communication between the discharge grooves and the screened pulp outlet, whereby the pulpis screened by .passing from the inlet grooves to the discharge grooves through said clearance space.

2. A pulp screen comprising, a casing having an inlet and a screened pulp outlet, pulp-screenthereof which bounds said clearance space, a portion of said grooves constituting inlet grooves and the remainder of the grooves constituting discharge grooves, means for delivering unscreened pulp from said casing inlet to the inlet grooves, means providing communication between the discharge grooves and the screened pulp outlet, said other member being provided with an opening communicating with the clearance space, and means to move said members relative-to each other and in a directlorsto bring the opening into registry with the inlet grooves successively, whereby when said opening is brought into registry with 3. A pulp screen having a casing provided with an inlet for the unscreened paper pulp and an outlet for the screened pulp, two concentric cylindrical screen members located in the casing and providing between them an annular clearance space of suflicient size for the fine acceptable portions of the unscreened pulp to pass therethrough but of insufficient size for the coarse unacceptable portion of such pulp to pass therethrough, one of said members having a plurality of grooves in the face thereof which is adjacent the other member, certain of said grooves constituting inlet grooves and the remainder of the grooves constituting discharge grooves, means by which unscreened pulp from the casing inlet is delivered to the inlet grooves, and means providing communication between the discharge grooves and the screened pulp outlet.

4. A pulp screen having a casing provided with an inlet for the unscreened paper pulp and an outlet for the screened pulp, two concentric cylindrical screen members located in the casing and providing between them an annular clearance space of sufficient size for the fine acceptable portions of the unscreened pulp to pass therethrough but of insuflicient size for the coarse unacceptable portion of such pulp to pass therethrough, one of said members having a plurality of grooves in the face thereof which is adjacent the other member, certain of said grooves constituting inlet grooves and the remainder of the grooves constituting discharge grooves, means pulp from the casing inlet is delivered to the inlet grooves, means providing communication between the discharge grooves and the screened pulp outlet, the other of said screen members having an opening communicating with said clearance space, and means to produce relative rotation between said screen members about their common axis, whereby said opening will be brought periodically into registry with each inlet groove.

5. A pulp screen comprising a casing having an inlet for unscreened paper pulp and a screened pulp outlet, two concentric cylindrical screen members within the casing and presenting between them a clearance space of sufficient size for the fine acceptable portion of the unscreened pulp to pass therethrough but of insufficient size for the coarse unacceptable portion of such pulp to pass therethrough, the outer screen member having in its inner face a plurality of parallel grooves, the alternate grooves constituting inlet grooves and the other grooves constituting discharge grooves, means providing a communication between the casing inlet and the inlet grooves by which unscreened pulp is delivered to said grooves, means providing communication between the discharge grooves and the screened pulp outlet, said inner screen member having an opening communicating with said clearance space, and means to rotate the inner member relative to the outer member.

6. A pulp screen comprising a casing having an inlet for unscreened paper pulp and a screened pulp -outlet, pulp-screening means within said casing comprising two concentric cylindrical screen members separated by a clearance space of su'flicient width for the acceptable portion of the unby which unscreened screened pulp to pass therethrough but of insumcient width for the coarse unacceptable portion of the pulp to pass therethrough, the outer of said screen members having in its inner face a circumferential row of vertically extending grooves and also having a pair of circumferential chambers, one of which is an inlet chamber and the other of which is a discharge chamber, the alternate grooves of said row communicating with the circumferential inlet chamber and the other grooves-of the row communicating with the circumferential discharge chamber, means to deliver pulp'irom the casing inlet to the inlet chamber, and means providing communication between the discharge chamber and the screened pulp outlet.'

7. A pulp screen comprising a casing having an inlet for unscreened paper pulp and a screened pulp outlet, pulp screening means within said casing comprising two concentric cylindrical screen members separated by a clearance space of willcient width for the acceptable portion of the unscreened pulp to pass therethrough but of insufllcient width for the coarse unacceptable portion of the pulp to pass therethrough, the outer of said screen members having in its inner face a plurality of circumferential rows of vertically extending grooves and also having a pair of circumferential chambers for each row of grooves, one chamber of each pair being an inlet chamber and the other being a discharge chamber, the alternate grooves of each row communicating with the corresponding circumferential inlet chamber and the remaininggrooves of each row communicating with the corresponding circumf erential discharge chamber, means to deliver unscreened pulp from the casing inlet to the various circumferential-inlet chambers, and means providing communication between the various discharge chambers and the screened pulp outlet.

8. A pulp screen comprising a casing having an inlet for unscreened paper pulp and a screened pulp outlet, pulp screening means within said casing comprising two concentric cylindrical screen members separated by a clearance space of sumcient width for the acceptable portion of the unscreened pulp to pass therethrough but of insufficient width for the coarse unacceptable portion of the pulp to pass therethrough, the outer of said screen members having in its inner face a plurality of circumferential rows of vertically extending grooves and also having a pair of circumferential chambers for each row of grooves, one chamber of each pair being an inlet chamber and the other being a discharge chamber, the alternate grooves of each row communicating with the corresponding circumferential inlet chamber and the remaining grooves of each row communicating with the corresponding circumferentiai discharge chamber, the space between the casing and the outer screen member being divided by partitions into inlet and discharge passages, the circumferential inlet chambers having communication with the inlet pas-sages and the circumferential discharge chambers having communication with the discharge passages, means providing a communication between the casing inlet and the inlet passages, and means providing communication between the discharge passages and the screened pulp outlet.

9. A pulp screen comprising a casing having an inlet for unscreened paper pulp and a screened pulp outlet, pulp-screening means within said casing comprising two concentric cylindrical screen clearance space, means 2 337 113 space for delivering unscreened paper pulp to the 5g member separated by a clearance space of slim cient width for the acceptable portion of the unscreened pulp to pass therethrough but of insuflimeans providing communication between the discharge chamber and-the screened pulp outlet,

said inner screen member having openings, and means to rotate said inner screen member to bring the openings into register with the inlet grooves successively whereby each inlet groove is periodically flushed out.

10. A pulp screen comprising two opposed walls spaced from each other to provide betweenthem a clearance space suflicient in size for the acceptable portion of unscreened paper pulp to pass therethrough but insuflicient in size for the unacceptable portion of such pulp to pass, one wall having therein a plurality of separate pockets all of which open into said clearance space, means other than the clearance space for delivering unscreened paper pulp to certain of said pockets, from which the pulp flows into the other pockets through the clearance space which is common to all of the pockets, a screened pulp outlet, and means other than the clearance space providing therethrough, the outer of which is an inlet chamber and] communication between said other pockets and the screened pulp outlet.

11. A pulp screen comprising a casing having an inlet and a screened pulp outlet, pulp-screening means within the casing comprising two opposed parallel walls separated from each other by a clearance space which is substantially coextensive with the walls and is of sufficient size for the acceptable portion of unscreened paper pulp stock to pass therethrough but insilificient in size for the unacceptable portion of such pulp to pass therethrough, one wall having therein both a plurality of inlet pockets, all of which open into said clearance space, and a plurality of .discharge pockets all or which open into said clearance space, said inlet and discharge pockets having communication with each other through the otherthan the clearance inlet pockets and means other than the clearance space providing communication between the discharge pockets and the screened pulp outlet.

12. A pulp screen ing means within the casing comprising two opposedparallel walls separated from each other by a clearance space which is substantially coextensive with said walls and which is of suificient size for the acceptable portion of unscreened paper pulp stock to pass therethrough but is insufiicient in size for the unacceptable portion of such pulp stock to pass therethrough, one of said 7 walls having therein a plurality oi inlet pockets, all of which communicate with the clearance space, and also having therein a plurality of disa charge pockets, all of which communicate with the clearance space, said inlet pockets and outlet pockets having communication with each other through said clearance space, means other than the clearance space for delivering unscreened pulp to the inlet pockets, means other than the clear-' ance space providing communication between the discharge pockets and the screened pulp outlet,

and means to give the two opposed walls alrelative movement without varying the dimensions of said clearance space.

13. A pulp screen comprising a casing having an inlet and a screened ing means within the casing comprising two opposed parallel walls separated from each other by a clearance space of suificient size for the acceptable portion of unscreenecl paper pulp stock to pass therethrough but insumcient in size for the unacceptable portion of such pulp to pass therethrough, one of the walls having a plurality of inlet openings therethrough communicating with the clearance rality of discharge openings therethrough communicating with said clearance space, means for delivering unscreened pulp to the inlet openings,

outlet.

WIIJRED F. MATHEWSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,185,794 Haug June 6, 1916 Knight Dec. 21, 1943 comprising a casing having an inlet and a screened pulp outlet, pulp-screenpulp outlet, pulp-screenspace and also having a plu- 

